For my own managed funds/indexes, I use https://m1finance.com, also with no fees.
You specify pies of funds with weights.
They automatically allocate funds and dividends to the underweight entries, and have 1 click for rebalancing.
It's not made for single-real time trading, there's one trading window each day.
Sure beats the spreadsheet and whole-share issues when I did it for free with Robinhood.